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From: Henson, Sam::(HENSNS) at ~FABRIK
Date: 9/3/96 4:40AM
To: Andrew P Magee at Rogers-MCD
Subject: Re: FAB:Cupric Chloride Etchant
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From: Henson, Sam
[log in to unmask] (Henson, Sam)
Date: Tue, Sep 3, 1996 4:40 AM
Subject: Re: FAB:Cupric Chloride Etchant
To: Magee, Andrew P
There is a design problem with some equipment. There is not enough
contact
time between the chlorine gas and the liquid. If you add the gas in
excess
of 500 Pounds per day flow rate then it liberates out. I have some
methods
dealing with this but I would need to know which model machine.
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From: RSedlak::(RSEDLK) at ~FABRIK
Date: 8/13/96 7:44PM
*To: 27=TechNet::[log in to unmask]::25=SMTP at ~FABRIK
Subject: Re: FAB:Cupric Chloride Etchant
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An extract from the IPC TechNet.
From: [log in to unmask]
Date: Tue, Aug 13, 1996 7:44 PM
Subject: Re: FAB:Cupric Chloride Etchant
To: TechNet
Chlorine is a gas, which is marginally
soluble in water. The more salts, all
other things being equal, such as pH, the
less soluble the Chlorine. So, you
could be creating Chlorine when the Copper
is low, and it is soluble enough
to not be given off.
One key question is do you monitor your ORP,
that is to say, actually keep a
continuous record of it?? If you are
getting serious spikes in an ORP
chart, you are creating Chlorine, whether
you smell it or not.
Another factor, that could be contributing
is the viscosity, and thus mixing
speed of the etchant. If the Copper is low,
the mixing speed of the components is
higher, and this will allow the Cuprous ion
to come into
contact with the Chlorine gas, and react
with it, and make it go away,
faster.
One of the factors that I have seen
personally that can contribute seriously
to this problem is the type (and horsepower)
of the pump making the additions. If the
pump is too powerful, and ANY centrifugal
pump I have ever
seen is too powerful, It will seriously
over-add before the ORP sensor tells
it to shut off. Best type of pump is a
bellows pump, and they should be
sized so that they are running a lot of the
time that panels are going down
the line. Never less than 20% of the time,
and more is better, up to even as
high as 70% of the time. This ensures slow
addition, so that the reactants
can circulate around enough to find the
Cuprous ion, and not have time to
say, "Hey, can't find no Cuprous, I'm
history!", and escape to the atmosphere.
Also, speaking of mixing, if you are running
more than one chamber, you
should have some serious horsepower mixing
the two sumps. This is best done
by pumping from the last chamber to the
first, and cascading back. I am
going to make a rough estimate that you want
one HP of pump circulating for
every etcher sump in a line.
And that is an absolute minimum.
Also, if you have more than one etcher sump,
you may want to add Chlorate and
HCl at more than one point.
If you would like more free opinions, which
some have said are worth almost
what you pay for them, e-mail, or call.
Rudy Sedlak
RD Chemical Company
415-962-8004
From: Gurian, Marshall
Date: Tue, Aug 13, 1996 3:03 AM
Subject: Re: FAB:Cupric Chloride Etchant To:
TechNet
I have two guesses Re: fuming with high
copper levels.
Guess 1: ORP reading becomes less sensitive
as copper levels get higher,
requiring more Cu(I) to trip ORP adder
point. This may encourage a slow control
response, allowing overdosing of oxidizer.
Guess 2: Conductivity controllers are set up
on a narrow response to conductance in a
very specific mixture where the only
significant variable is HCl. High Cu
may add to the conductivity and cause acid
to fail to add. This will definitely
throw the system out of balance, either
causing overadd of oxidizer (liberating
gas when some HCl is added) or some other
phenomenon.
I may be able to be more complete with more
detailed operation info.
Marshall Gurian
Coates ASI
e-mail: [log in to unmask]
Date: Tue, Aug 13, 1996 3:40 PM
Subject: RE: FAB:Cupric Chloride Etchant To:
"[log in to unmask]" Look in Coombs, Handbook
of Printed Circuits 3 rd edition on page
14.15 at paragraph 14.4.3 for the chemical
reactions. I think you will find that the
amount of copper is not as important as the
state of the copper, if there is no
more cuprous ions to be converted to cupric
then the chemistry you are still
adding is there to react. Or if you are
really putting through the volume you
could be overwhelming your cooling system
allowing the temperature to rise and
liberating gasses from solution. In short
you have excess chlorate and excess
hydrochloric acid and should anticipate
chlorine gas and hydrogen chloride gas
as a minimum as a result. If the solution
is bright green the correct response
is in fact to add copper clad material.
This converts some of the cupric back
to cuprous and that regenerates knocking
down the excess chemistry.
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From: [log in to unmask]
To: [log in to unmask]
Subject: FAB:Cupric Chloride Etchant Date: Tuesday, August 13, 1996
11:01AM
We etch inner layers using Cupric Chloride Etchant. We control
the chemistry with ORP and Conductivity probes. The ORP adds
Sodium Chlorate and the Conductivity controls HCl adds.
We have experienced gas generation (chlorine or HCl fumes) when
both the ORP and Conductivity are in control. The gas/fume
release occurs when the copper gets as high as 33 - 35 ounces
per gallon.
Standard procedure is to feed copper into the system when a
chemical out of balance situation results in gas generation.
Clearly in this case this would be the wrong thing to do.
Can anyone explain the chemical reaction behind a release of
gas/fumes when the copper is high?
From: [log in to unmask] (Henson, Sam)
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